This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/SE98/01201 which has an International filing date of Jun. 18, 1998, which designated the United States of America.
The present invention relates to a method for automatized dose planning in stereotactic radiosurgery.
In neurosurgical treatment of tumours, vascular deformities, and similar malformations in the brain, stereotactic radiosurgery techniques are often used, including for example gamma radiation from Cobolt-60 sources, such as the one commercially available under the denomination GammaKniven (Gamma Knife). Preferably, a plurality of sources of this kind are distributed around the head of the patient. By means of a collimator, the radiated beams are focused to a small spherical area in the brain. The diameter of the sphere is a matter of choice, as is also the duration of the radiation (weight), and by superposing within the brain the doses issued from several such irradiation points it becomes possible to produce a dose-radiation field wherein the dose received by the tumour is maximized while at the same time the dose received by surrounding tissue is minimized. Today, dose planning is effected entirely manually by physicians or hospital physicists who position radiation points, known as shots, inside the tumour and compare the dose distribution with the extension of the tumour by studying tomograms of the brain. It is likewise possible to seek assistance from a computer program, such as the commercially available GammaPlan program, which allows two or three dimensional viewing of target volumes and dose distribution as well as storage of lamina images of the brain that are obtained by imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI) and angiographic imaging, but wherein the choice of irradiation points is effected entirely manually. This essentially manual process is time-consuming and in addition places high demands on the experience and the skill of the individual performing the dose planning.
Attempts have also be made to effect dose planning by automated means. One such method was based on the idea of presuming the shots to be spheres with which one tried to fill the target volume optimally. This method functioned reasonably well as long as only two dimensions were involved but could not be applied to three-dimensional viewing. Another tested method involved continuous displacement of the shots through the target volume, to thus obtain a superposed dose which covered the target volume. This method functioned well in theory but has proved unsuccessful so far because it is not yet possible to continuously displace the shots through the volume.
Consequently it is an object of the present invention to provide a method for automatized dose planning for stereotactic radiosurgery, by means of which the problems and disadvantages outlined above are completely or at least partly eliminated.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.